On July 19, 1879 in Las Vegas, New Mexico a drunk Mike Gordon—either because of a problem with a girl or bad luck at the gaming tables—started randomly firing his gun outside a dance hall.
Somebody—maybe several somebodies—joined in the shooting. After things calmed down, Gordon was found injured; he died a few hours later. Legend says that Doc Holliday was the man who took out Gordon, in what would be the dentist’s first killing. There’s no evidence of that. And a coroner called it a justifiable homicide by a person unknown.